Hydraulic circuits are often used to control the operation of hydraulic actuators of work machines. These hydraulic circuits typically include valves that are fluidly connected between a pump and the actuators to control a flow rate and direction of pressurized fluid to and from chambers of the actuator. In some instances, multiple actuators may be connected to a common pump causing undesirable pressure fluctuations within the hydraulic circuits during operation of the actuators. In particular, the pressure of a fluid supplied to one actuator may undesirably fluctuate in response to operation of a different actuator fluidly connected to the same pump. These pressure fluctuations may cause inconsistent and/or unexpected actuator movements. In addition, the pressure fluctuations may be severe enough and/or occur often enough to cause malfunction or premature failure of hydraulic circuit components.
One method of reducing these pressure fluctuations within the fluid supplied to a hydraulic actuator is described in U.S. Pat. No. 5,878,647 (“the '647 patent”) issued to Wilke et al. on Mar. 9, 1999. The '647 patent describes a hydraulic circuit having two pairs of solenoid valves, a variable displacement pump, a reservoir tank, and a hydraulic actuator. One pair of the solenoid valves includes a head-end supply valve and a head-end return valve and connects a head end of the hydraulic actuator to either the variable displacement pump or the reservoir tank. The other pair of solenoid valves includes a rod-end supply valve and a rod-end return valve and connects a rod end of the hydraulic actuator to either the variable displacement pump or the reservoir tank. Each of these four solenoid valves is associated with a different pressure compensating check valve. Each pressure compensating check valve is connected between the respective solenoid valve and the actuator to control a pressure of the fluid between the associated valve and the actuator.
Although the multiple pressure compensating valves of the hydraulic circuit described in the '647 patent may reduce pressure fluctuations within the hydraulic circuit, they may increase the cost and complexity of the hydraulic circuit. In addition, the pressure compensating valves of the '647 patent may not control the pressures within the hydraulic circuit precise enough for optimal performance of the associated actuator.
Additionally, hydraulically actuated pressure compensating valves may cause undesirable pressure fluctuations within the hydraulic circuit if biased by significantly low pressure signals. Such pressure signals may communicate significantly low pressure pulses to the pressure compensating valve that could cause rapid movement of the pressure compensating valve element. This rapid movement may result in a pressure surge through the hydraulic circuit and, if communicated to the actuator, may cause undesirable and/or jerky operation of the actuator.
The disclosed valve is directed to overcoming one or more of the problems set forth above.